The Creek Conditions Reports are designed to summarize water quality conditions in 17 tidal creek basins. These coastal creeks, many of which are fed by drainage canals, flow downstream to bays and eventually to the Gulf of Mexico. Each creek has upstream segments that are freshwater, and downstream segments that are predominantly marine. “Predominantly” because tidal influence causes the salinity in each segment to vary throughout the course of the day. “Predominantly freshwater” and “predominantly marine” streams are assessed differently by environmental regulators, with different parameters used to assess water quality, and different pollution limits assigned.
The Water Chemistry Ratings section shows sampling history and trend information for several primary water quality indicators. The rating for each is determined by the sampled values for that indicator for the year shown. (See “Methods” section below for more information about each indicator.)
The rating system used is based on Numeric Nutrient Criteria adopted by the Florida Department of Environmental Protection in accordance with the Clean Water Act. These rules may be updated over time; a summary of the current standards may be found in Florida Administrative Code, Chapter 62-302.530, "Table: Surface Water Quality Criteria".
The Five-Year Rolling Average illustrates the general tendency of each water quality indicator, using a six-month moving average. The graph plots the arithmetic mean of sample values collected during the previous six-month period. A moving average tends to moderate temporary spikes and dips in a graph and instead shows a general trend. The Method Detection Limit is the lowest concentration which can be measured for a given laboratory method. The chart accompanying the graph gives an idea of the historic range of values for the indicator, and where data in the scored year fall with respect to that range. You can use the “Download Data” link to see all the individual data samples that were used in creating the ratings, charts and graphs shown on the Creek Conditions Report.
Water quality data for predominantly marine stream segments are aggregated and rated separately from the data for predominantly freshwater segments. Each individual water quality parameter is rated for both the upstream (freshwater) and downstream (marine) portions of a creek, and based on these the entire creek is given a rating. Learn More about how these ratings are assigned »
In addition to the primary indicators used in establishing creek ratings, other parameters related to water quality also are displayed. These include biochemical oxygen demand, apparent color, E. coli, ammonia, Kjeldahl nitrogen, nitrate/nitrite, pH, specific conductance, water temperature, land use/land cover, impervious surfaces, salinity, turbidity, rainfall and oysters.
According to the Florida Administrative Code:
“Predominantly fresh waters” shall mean surface waters in which the chloride concentration is less than 1,500 milligrams per liter (mg/L) or specific conductance is less than 4,580 micromhos per centimeter (µmhos/cm). Measurements for making this determination shall be taken within the bottom half of the water column. [F.A.C. 62-302.200(29)]
“Predominantly marine waters” shall mean surface waters in which the chloride concentration is greater than or equal to 1,500 mg/L or specific conductance is greater than or equal to 4,580 µmhos/cm. Measurements for making this determination shall be taken within the bottom half of the water column. [F.A.C. 62-302.200(30)]
“Numeric nutrient criteria” are the pollutant concentration limits used by environmental regulators to determine whether a water body is “impaired” for its established uses (such as potable water supply, shellfish harvesting, recreation, navigation, or agricultural use). These rules are defined in F.A.C. 62-302.532 and 62-302.533 and explained more fully in “Implementation of Florida’s Numeric Nutrient Standards”, dated April 2013.